Memory disk "a la mfsroot"?

[Pierre-Luc Drouin]

Hi,

I would like to know if there is a mount command that allows to create a 
memory disk that can be initialized from a file. What I am looking for 
is something like mount_mfs -F, but that does not modify the actual 
file. I know what I could easily to this by copying the content of the 
file to the memory disk, but I am looking for a solution that can be 
configured via fstab.

Thanks!